Auger type poultry chillers have been in use for more than 40 years. The equipment includes a nominally horizontal semi-cylindrical tank with an Archimedes screw running down the length of the tank. In this context, the screw is often called an auger.
A conventional auger type poultry chiller 10 is illustrated in FIGS. 1-3. A tank 12 is filled with chilled water, typically to a level at or slightly above the top of the auger shaft 22. The chilled water may be supplied from a heat exchanger 40. Freshly slaughtered and eviscerated birds are introduced into the tank 12 at an inlet end 14 and conveyed to the opposite outlet end 16 by turning the auger 20 (e.g., using a motor that is operatively coupled to the auger 20). The auger 20 is designed such that the water in the tank 12 is not conveyed along with the birds. Instead, water flows around the edges of the auger flight or through passages in the flight provided for this purpose to effectively move the water in a direction counter to the movement of the birds. With one exception described below, the gaps and passages through which water flows are too small for birds to pass through back toward the inlet end of the tank.
Auger chillers are often in excess of 60 feet in length. However, in order to facilitate fabrication and transport, designers generally avoid auger spans that exceed approximately 30 feet in length. Consequently, the screw must be supported at intermediate points along its length. This support has historically been provided by so-called hanger bearings (see, e.g., the hanger bearing 30 in FIGS. 2 and 3). The hanger bearing includes a bearing element—usually of the journal type—installed around a coupling shaft that joins two adjacent sections of the auger 24, 26 (FIG. 3). The bearing element is suspended from above by a hanger 34 that is fixed to a support member 32 at the top edge of the tank 12 (FIG. 3).
In the prior art, hangers have been fabricated from robust material shapes such as 4 inch square tubing. While providing relatively rigid support for the bearing and auger, such large structural members require a correspondingly large gap between one section of the auger and the next. It is not unusual for this gap to be 10 inches or larger in width. Such a gap is large enough for birds to pass through from one side of the auger flight to the next. Such “leakage” of birds can interrupt the sequence in which birds are processed and introduce variability in the time birds spend in the tank.
Another problem is that the large gap allows birds to remain in the chiller after processing is complete. These birds must be removed by handling personnel prior to cleaning the chiller tank. In addition to increased time and expense associated with the cleanup process, expense is incurred due to loss of product at the hanger bearing.
The need for better chiller performance at intermediate bearings is described in U.S. Pat. Nos. 6,722,490 and 6,951,273, the disclosures of which are incorporated herein in their entireties. Interruptions in the auger flight allow birds to move between compartments in the Archimedes screw. The '490 and '273 patents address a bearing design that would take up less space, but neglect to detail the application of this bearing and techniques to minimize the gap in the auger flight.
The present inventor considered one strategy in which the flight of the downstream auger section matches that of the upstream auger section as though a continuous flight had been made and then an interval was removed to allow the hanger support to pass through (FIG. 4A). However, due to the relatively short pitch (axial distance from one flight to the next) used in auger chillers, simply deleting a segment from a continuous flight along a short axial distance would result in a broad opening in the transverse direction (FIG. 4B). Such an opening can allow birds to pass through with relative ease.
The present inventor considered another approach in which the edges at the end of the upstream and downstream flights are aligned such that the distance between the two edges is minimized (FIGS. 5A and 5B). This creates a “step” for the product to overcome at the hanger. Rather than facing an inclined plane that encourages the bird to move primarily along the length of the tank, the step presents the product with a blunt face that encourages the bird to move circumferentially around the tank. As the gap in the flight approaches the hanger, it can even create a scissors action that tends to damage the product (FIGS. 5C and 5D). Potential damage from this pinching action is one reason wide gaps have been tolerated in prior art chillers even though processing consistency is compromised. A wide gap allows a bird to be pushed through rather than damaged.
The approaches described in reference to FIGS. 4A, 4B and 5A-D could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise described herein, the approaches described in reference to FIGS. 4A, 4B and 5A-D are not prior art to claims in this application and any application claiming priority from this application, are not admitted to be prior art by inclusion in this section, and may be attributed to the present inventor's appreciation of the problem to be solved.